Palladino Pasquale, Torrini Francesca, Scarano Simona, Minunni Maria
Department of Chemistry 'Ugo Schiff', University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino, Italy.
Anal Bioanal Chem. 2020 Nov;412(28):7861-7869. doi: 10.1007/s00216-020-02918-9. Epub 2020 Sep 1.
Sanitizing solutions against bacterial and viral pathogens are of utmost importance in general and, in particular, in these times of pandemic due to Sars-Cov2. They frequently consist of chlorine-based solutions, or in the direct input of a certain amount of chlorine in water supply systems and swimming pools. Colorimetry is one of the techniques used to measure the crucial persistence of chlorine in water, including household chlorine test kits commonly based on colorimetric indicators. Here, we show a simple and cheap colorimetric method based on 3,3',5,5'-tetramethylbenzidine (TMB), commonly used as chromogenic reagent for enzyme-linked immunosorbent assays. TMB is converted by chlorine to a colored molecule through a pH-dependent multi-step oxidation process where the chromaticity of TMB is directly proportional to chlorine content. This molecule offers several advantages over other commonly used reagents in terms of safety, sensitivity, and, peculiarly, hue modulation, giving rise to the detection of chlorine in water with a multi-color change of the indicator solution (transparent/blue/green/yellow). Moreover, through the appropriate setting of reaction conditions, such coloration is finely tunable to cover the range of chlorine concentration recommended by international health agencies for treatment of drinking water and swimming pools and to test homemade solutions prepared by dilution of household bleach during health emergency events such as during the current pandemic. Graphical abstract.
针对细菌和病毒病原体的消毒溶液总体上至关重要，尤其是在当前因新冠病毒（Sars-Cov2）大流行的时期。它们通常由含氯溶液组成，或者是在供水系统和游泳池中直接加入一定量的氯。比色法是用于测量水中氯关键残留量的技术之一，包括通常基于比色指示剂的家用氯测试试剂盒。在此，我们展示了一种基于3,3',5,5'-四甲基联苯胺（TMB）的简单且廉价的比色法，TMB通常用作酶联免疫吸附测定的显色试剂。通过pH依赖的多步氧化过程，氯将TMB转化为有色分子，其中TMB的色度与氯含量成正比。与其他常用试剂相比，该分子在安全性、灵敏度方面，特别是在色调调节方面具有诸多优势，可通过指示剂溶液的多色变化（透明/蓝色/绿色/黄色）实现水中氯的检测。此外，通过适当设置反应条件，这种显色可精细调节，以覆盖国际卫生机构推荐的用于饮用水处理和游泳池的氯浓度范围，并用于检测在当前大流行等健康紧急事件期间通过稀释家用漂白剂制备的自制溶液。图形摘要。
